同时指定TypeTag时如何指定Scala类型参数约束

Question

I can capture the type of some type parameter of a class like so:

import scala.reflect.runtime.universe._

case class X[T:TypeTag]() {
   val typ = typeOf[T]
}

But how can I do the same if I want to enforce a type constraint:

trait SomeClass

case class X[T<:SomeClass]() {
  val typ = typeOf[T]
}

This doesn't work:

case class X[T<:SomeClass with TypeTag]() {  // TypeTag takes parameters
  val typ = typeOf[T]
}

neither does:

case class X[T<:SomeClass with TypeTag[T]]() {  

  val typ = typeOf[T]
}

X[String]()// type arguments [String] do not conform to method apply's type parameter bounds [T <: SomeClass with reflect.runtime.universe.TypeTag[T]]

Answer 1

scala> case class X[T <: SomeClass : TypeTag]() { 
  val typ = typeOf[T] 
}
defined class X